1. Field of the Invention
This invention relates to the control of automated equipment, and in particular to a control system which operates remote from the master control panel of the automated equipment.
2. Description of the Prior Art
Most automated manufacturing systems are presently equipped with sensing devices which will detect a variety of potentially dangerous operating conditions. Upon detection, an automated system will cease to operate or will retract to a home position as a result of a misplaced workpiece, programming error, or a foreign object entering into the unit's working environment. These sensing devices use a variety of probes, limit switches, and ultrasonic and photoelectric proximity switches. During normal operations, these sensors usually provide adequate protection from most malfunctions.
However, a danger is present when automated equipment, or more specifically a robotic device, is being programmed manually by a technician. Programming may take place by a variety of methods, but in most cases, proximity sensors and switches are deactivated to allow the technician to be in close contact with the robotic device. Programs may be input to the control unit by means of a programming pendant which is connected to the master control panel of the robotic device by a cable. In addition to programming functions, the pendant may possess a "soft stop" or "cycle hold" control function and a "hard stop" control function. These two control functions also usually appear on the master control panel.
The "soft stop" or "cycle hold" is activated when the technician wishes to jog the unit or interrupt the system during normal operations. Upon reactivation of the "soft stop" or "cycle hold", the system will resume the normal operating cycle. The "hard stop" function is only activated when the operator or technician perceives a serious malfunction within the system. Activating the "hard stop" will cause the unit to stop by deactivating the program and disconnecting the power from the various drive functions. In some cases the program will be lost from the memory. Programming methods other than the pendant type exist, but most control units regardless of their design possess these two distinct methods of controlling the systems movement.
Automated systems travel at various speeds depending upon the application. Some systems move as fast as 50 mph. As a result, an individual can be seriously injured if he does not react with the proper response in an emergency situation. If a technician actually carries the control pendant, he possesses the capability to control the unit's operational status. However, the control pendant with its attached cabling is often cumbersome and difficult to carry when the technician is working around the robotic device. The cable sometimes will become entangled in the equipment and the operator may be tempted to leave the pendant behind in order to make it easier to work on the equipment. In addition, the cable may be placed in a position where it can be accidentally damaged or severed by the operation of the equipment. If the programming pendant is not at hand or out of reach, or if the cable connecting the pendant has been damaged or severed, an individual has no method of quickly reacting to a program error or system malfunction.
Existing systems also have a limitation in that the "soft stop" or "cycle hold" may be cyclicable. If this control is activated while the equipment has been stopped or held, the actuation of the control will have the effect of reactivating the equipment so that movement resumes. Thus, if a technician operates the "soft stop" or "cycle hold" to stop the equipment and then inadvertently reactivates the control, the equipment may be inadvertently restarted, and the technician may be seriously injured.
The problem of reactivating the "soft stop" may be overcome by having the "soft stop" control on the pendant capable of only stopping the equipment and not restarting the equipment. However, this requires the technician to leave the equipment area and return to the master control panel to restart the equipment every time it is stopped.